[lld-macho] Fixed crashes when linking with incompatible-arch archives/

Two changes:
 - Avoid crashing in predicate functions.
   Querying the property of the Symbols via these is*() functions shouldn't crash the program - the answer should just be "false".
   Currently, having them throw UNREACHABLE already (incorrectly) crash certain code paths involving macho::validateSymbolRelocation() .

 - Simply ignore input archives with incompatible arch (changes from PRESIDENT810@)

Differential Revision: https://reviews.llvm.org/D156468